Artificial muscles restore ability to blink

Emma Woollacott, 18th January 2010

Surgeons at the UC Davis Medical Center have for the first time used artificial muscles, helping patients with facial paralysis to blink.

The team says the technique, which uses a combination of electrode leads and silicon polymers, could be used to develop synthetic muscles to control other parts of the body.

"This is the first-wave use of artificial muscle in any biological system," said Travis Tollefson, a facial plastic surgeon in the UC Davis Department of Otolaryngology. "But there are many ideas and concepts where this technology may play a role."

Eyelid paralysis is currently treated either by transferring a muscle from the leg into the face or by suturing a small gold weight inside the eyelid. Neither is terribly pleasant.

But Tollefson and his colleagues used an electroactive polymer artificial muscle (EPAM) which acts like a human muscle by expanding and contracting, based on variable voltage input levels.

The surgeons inserted a sling made of muscle fascia or implantable fabric around the eye, and attached it to a battery-operated artificial muscle. They found that the artificial muscle was easily strong enough to close the eyelid.

The muscle itself was developed by engineers at SRI International. Inside is a piece of soft acrylic or silicon layered with carbon grease. When a current is applied, electrostatic attraction causes the outer layers to pull together and squash the soft center, expanding the artificial muscle. The muscle contracts when the charge is removed and flattens the shape of the sling, blinking the eye. When the charge is reactivated, the muscle relaxes and the soft center reverts back to its original shape.

"The amount of force and movement the artificial muscle generates is very similar to natural muscle," Tollefson said.

For patients who have one functioning eyelid, a sensor wire threaded over the normal eyelid could detect the natural blink impulse and fire the artificial muscle at the same time. For patients lacking control of either eyelid, an electronic pacemaker similar to those used to regulate heartbeats could blink the eye at a steady rate, and be deactivated by a magnetic switch.

The researchers are now refining the technique, and reckon it should be available for patients within five years.